ADFGVX cipher

The cipher used by German Army during World War I

https://en.wikipedia.org/wiki/ADFGVX_cipher

Module CheckADFGVX_Cipher {
	Class cipher {
	Private:
		buffer a as byte*36
		b="ADFGVX"
		key="ABCDEFGHIJK"
		orderkey="ABCDEFGHIJK"
		map=list
		map2=list
		module preparemaps {
			for i=0 to 5
				jj=0
				for j=i*6 to j+5
					.map(chr$(.a[j]))=mid$(.b, i+1,1)+mid$(.b,jj+1, 1)
					.map2(mid$(.b, i+1,1)+mid$(.b,jj+1, 1))=chr$(.a[j])
					jj++
				next
			next			
		}
	Public:
		Module SetRandom (&returnvalue) {
			return .a, 0:=str$("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
			for i=1 to 100
				c=random(0, 35):d=c
				while c=d {d=random(0, 35)}
				 byte o=.a[c]
				.a[c]<=.a[d]
				.a[d]<=o
			next
			returnvalue=chr$(eval$(.a)) ' convert to UTF16LE
			.preparemaps	
		}
		Module SetSpecific (that$){
			return .a, 0:=str$(Ucase$(that$))
			.preparemaps		
		}
		Module SetKey (.key as string) {
			.key<=ucase$(.key)			
			if len(.key)<7 or len(.key)>12 then Error "Key has not proper length"
			if filter$(.key, "ABCDEFGHIJKLMNOPQRSTUVWXYZ")<>"" then
				Error "Key has bad letters"
			end if
			dim aa(1 to len(.key))
			for i=1 to len(.key):aa(i)=mid$(.key,i,1):next
			.orderkey<=aa()#sort()#str$("")				
		}
		Module Display {
			Print "The 6 x 6 Polybius square:"		
			Print "  | A D F G V X"
			Print "---------------"
			for i=0 to 5
				Print mid$(.b,i+1,1)+" | ";
				jj=0
				for j=i*6 to j+5
					print chr$(.a[j]);" ";
					jj++
				next
				print
			next
			Print "Key:";.key
		}
		Function Encrypt(p as string) {
			crypted=""
			for i=1 to len(p)	
				crypted+=.map$(mid$(p,i,1))
			next
			m=1
			encrypted=""
			For i = 1 To Len(.key)
				ch = Mid$(.orderkey, i, 1)			
				For j = Instr(.key, ch) - 1 To Len(crypted) - 1 Step Len(.key)
					encrypted += Mid$(crypted, j + 1, 1)
					if m mod 5=0 then encrypted += " "
					m++
				Next
			Next
			=encrypted
		}
		Function Decrypt(p as string) {
			p=filter$(p, " ")
			decrypted=""
			m=1
			dim b$(len(p))
			For i = 1 To Len(.key)
				ch = Mid$(.orderkey, i, 1)
				For j = Instr(.key, ch) - 1 To Len(p) - 1 Step Len(.key)
					b$(j)=mid$(p, m, 1)
					m++
				Next
			Next
			for i=0 to len(b$())-1 step 2
				decrypted+=.map2(b$(i)+b$(i+1))	
			next
			=decrypted	
		}
	}
	ADFGVX=cipher()
	for ADFGVX {
		.SetSpecific "A9GKMF1DQRSBVX8Z0WTEJLOPY5U4CN2H76I3"
		.SetKey "volcanism"
		.Display
		encode=.Encrypt("ATTACKAT1200AM")
		Print "Encoded: ";encode
		Print "Decoded: ";.Decrypt(encode)
		Rem { ' using randomblock
			thisblock=""
			.SetRandom	 &thisblock
			Print "Random Block:";thisblock
			.Display
			encode=.Encrypt("ATTACKAT1200AM")
			Print encode
			Print .Decrypt(encode)
		}	
	}
} 
CheckADFGVX_Cipher